Hydraulic support device in a paper making machine

ABSTRACT

A hydraulic support device in a paper making machine for supporting a first beam (52) on a second beam (53), having a pressure cushion (54) between the two beams. The pressure prevailing in the pressure cushion is variable but it is uniform over the entire length of the pressure cushion. The pressure cushion (54) rests on a contact surface of the first beam (52). The width (b) of the contact surface as seen in cross section is less than the total width (B) of the pressure cushion (54). A free space (55) into which a loop of the pressure cushion (54) can penetrate is provided on each side of the contact surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hydraulic support device forsupporting a first beam on a second beam which extends parallel thereto.

2. Description of the Related Art

There are two fundamentally different fields of use for such a hydraulicsupport device:

1. One of the two beams is part of a flow guide wall, for instance of ahead box of a paper making machine. Here the purpose of the hydraulicsupport device is to maintain the flow guide wall free of flexure. Thepressure of the fluid (namely, the fiber suspension) is transmitted herefrom the flow guide wall via the pressure cushion to the other beam.This beam is connected by flexurally elastic elements to thefirst-mentioned beam only at its two ends and can bend freely under thesupport force of the pressure cushion. Thus, no means are provided forcoupling the beams at locations along the beams which are between thetwo ends. See for instance, Federal Republic of Germany OS 36 14 302,which is equivalent to U.S. Pat. No. 4,770,745. When the one beam, whichis part of the flow guide wall, bends for any reason, the pressure ofthe pressure cushion is changed in such direction as to cancel the bend.

2. One of the two beams is developed as a ledge which is moveable inoperation for the resilient supporting of a wire screen in the region ofthe double wire zone of a paper making machine; in this connection it isdisplaceable or swingable with regard to the other beam. In such case,the hydraulic support device acts as a resilient lift device. Any changein the pressure of the pressure cushion therefore produces a change, forinstance, in the distance between the two beams and a change in theforce which is applied by the ledge against the wire. Thus, no means areprovided for limiting a change in the distance between the two beamswhile there is pressure in the pressure cushion and during pressing ofthe contact surfaces on the pressure cushion. See, for instance,International Application WO 89/02499.

From FIGS. 1 to 5 of the above-cited German OS 36 14 302 it is known touse a tube as pressure cushion. This tube, seen in cross section, ispressed more or less flat depending on the distance between the twobeams. The distance between the two beams is generally not the same overthe length of the beams, primarily because the one beam is bent relativeto the other beam. This has the result that the supporting force of thepressure cushion along the length of the beams (i.e. over the width ofthe machine) varies relatively greatly from a desired constant value.

From FIGS. 6 to 8 of Federal Republic of Germany OS 36 14 302 it isknown that the individual pressure cushion can have a bellows-likeprofile with side walls folded inward. In this way, it has beenattempted to eliminate the aforementioned disadvantage. In other words,by this proposal it was attempted to obtain a constant value of thesupport force over the width of the machine despite the differentdistance between the two beams over the width of the machine. However,this proposal is also unsuccessful even though the width of the contactsurface between the pressure cushion and the beams remains the same withdifferent distances between the two beams. The reason for this is thatthe internal pressure in each inclined section of the side wall producesa component of force which represents a disturbing force actingperpendicularly on the adjacent contact surface. The amount of thisdisturbing force depends on the inclination of the section of the sidewall and thus on the distance between the two beams. Anotherdisadvantage of this known embodiment is that it is very difficult toproduce a pressure cushion which has such inwardly folded side walls andnevertheless withstands the necessary internal pressures.

SUMMARY OF THE INVENTION

The object of the present invention is further to improve theabove-described hydraulic support device in such a manner that thesupporting force produced by the pressure cushion does not change, or atleast changes only slightly, when the distance between the two beams isdifferent along the length of the beams (for instance, as a result ofthe the two beams changes in operation for some other reason. There aretwo parallel beams and at least one adjustable pressure cushionextending longitudinally and in contact with the contact surfaces of thetwo beams. The invention sees to it that--at least on one of the twobeams--the pressure cushion exerts a supporting force which is at leastapproximately constant over the length of the beam under all operatingconditions which occur. This is achieved in the manner that, seen incross section, a free space is present on both sides of the contactsurface the width of which is less than the total width of the pressurecushion and a loop of the pressure cushion which may be in the form of apressure filled tube, extends into such free space. The supporting forceis now formed by the pure pressure force, which depends on the internalpressure and on the width of the contact surface, and by clamping forceswhich result from the internal pressure within the loops. If now, withthe same internal pressure, the distance between the two beams changes,the width of the contact surface remains at least approximately thesame; furthermore, the clamping forces change only slightly or (inparticularly favorable cases) not at all.

Compared with the above-mentioned known forms of pressure-cushions aconstant value of the supporting force is obtained, at least in goodapproximation, along the length of the beams even if the distancebetween the two beams is not the same at different places.

The features set forth above are, to be sure, already known from U.S.Pat. No. 4,559,105, but that patent concerns an entirely different typeof hydraulic support device. There is involved there a ledge whichserves to support a wire, but the ledge is not arranged resiliently. Theledge rests on a beam of C-shaped cross section which is placed over abeam of T-shaped cross section. In order to facilitate the assembling ofthe two beams, a certain play is provided. In order to exclude the playduring operation, the two beams are clamped together by a pressurecushion so that they form a form-locked unit in operation. Thus, theknown construction cannot make use of the above-described advantages ofthe present invention.

A side surface at each side of each beam and spaced away from the sideof the contact surface defines a free space for the pressure cushion.

Coupling means at the longitudinal ends of and between the beamsflexurally permit the beams to tilt traversely to their lengths.

Advantageous features of the invention are explained below withreference to embodiments shown in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a longitudinal section (along the line I--I FIG. 1B)through the head box of a paper making machine having a hydraulicsupport device provided between two beams.

FIG. 1A shows a portion of FIG. 1 with enlarged distance between thebeams (section along the line A--A of FIG. 1B).

FIG. 1B is a partial view seen in the direction of the arrow B in FIG.1.

FIG. 2 is a partial cross section through a ledge for the resilientsupporting of a wire screen in a double-wire arrangement.

FIG. 2A shows the ledge of FIG. 2 in a position drawn back from thewires.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The head box shown in FIGS. 1, 1A and 1B serves, as is known, forfeeding a machine-wide jet of pulp onto the endless wire/screen/or wire9 of a paper manufacturing machine. The wire 9 travels inter alia over abreast roll 8 arranged at the head box and over a wire table 7. Forforming the jet of pulp, the head box has a nozzle-like outlet channel 4which is limited by a lower stationary channel wall 22 and an upperchannel wall 25, 26. The upstream part 25 of the upper channel wall isalso stationary in the embodiment shown, i.e. it is part of thestationary head box housing 24. The downstream part 26 of the upperchannel wall is moveable in order to be able to change the size of theinside opening of the outlet slot 23. This mobility is preferablyobtained in the manner that the downstream part 26 is fastened by ahinge 27 to the upstream part 25.

In order to stiffen the moveable channel wall 26, a beam, namely aso-called channel-wall support 16, is placed on its top and rigidlyattached to it (for instance, by welding). The channel-wall support 16is preferably of box shape; it has a front wall 17, a rear wall 18, andan upper wall 19.

Above the channel-wall support 16 there is another beam, namely asupport beam 31, which is also of box shape. Both beams 16 and 31 areshown in cross section in FIG. 1; they extend over the entire width KBof the machine between sides 49 (FIG. 1B) and are attached by means offlexibly soft connecting elements 30 merely at their two ends (i.e. onthe operator side and on the driven side of the paper machine). Thesupport beam 31 has a pin 33 on both of its ends. With the pin there isconnected a lift device of which only a spindle 13 and a bearing bracket28 fastened to the housing 24 are diagrammatically in FIG. 1.

Between the channel wall support 16 and the support beam 31 there is apressure cushion 32, preferably in the form of a tube, which can beacted on by a liquid under pressure. It would also be conceivable hereto use a membrane instead of the tube. The pressure prevailing in thepressure cushion 32 is variable (by means of control elements, notshown). It can for instance be so dimensioned, with due consideration ofthe liquid pressure prevailing in the outlet channel 4 and of the weightitself of the moveable channel wall 26 and of the channel wall support16, that the moveable channel wall 26 is completely free of bend. Inthis connection, the support beam 31 is bent slightly upwards, as can benoted from FIG. 1B. It is advisable in this case to regulate the liquidpressure as a function of a continuous measurement of the bending of thechannel wall support 16 (as known per se from U.S. Pat. No. 3,994,773,incorporated herein by reference. As shown in that reference, themeasuring device 60 in FIG. 1 hereof continuously detects the bending ofdeflection of the channel wall support 16 and emits a correspondingsignal via line 61 to valve 62. The valve 62 is arranged in a liquidfeed line connected to the cushion 32. Therefore, the valve 62 is ableto regulate the cushion pressure as a function of the bending of thesupport 16.

Heat-treatment channels 38 and 39 are provided within the channel wallsupport 16.

It is diagrammatically indicated that the outermost end 26' of themoveable channel wall 26 can be deformed locally as known per se, bymeans of a plurality of individually actuatable spindles 11. In thisway, minor local corrections of the inner size of the outlet slot 23 canbe effected.

The upper wall 19 of the channel wall support 16 is provided on its topwith a ledge 19'. The top of this ledge 19' forms a so-called contactsurface of the channel wall support 16 against which the pressurecushion 32 lies. As shown in FIG. 1, the width of the contact surface ofthe ledge 19' is smaller than the total width of the pressure cushion32. In this way, a free space 35 remains on each side of the ledge 19'(FIG. 1A), the free space being more or less filled by a loop of thepressure cushion 32. The support beam 31 has a lower wall 42 and sidewalls 43. The latter extend downward beyond the lower wall 42 wherethere they support the pressure cushion 32 on its side. The width of thelower wall 42 is thus substantially the same as the total width of thepressure cushion. In other words, almost the entire outer surface of thelower wall forms the contact surface of the support beam 31 for thepressure cushion 32.

FIG. 1A shows the pressure cushion 32 and the adjoining parts of the twobeams 16 and 31 at a point of the head box where, as a result of bendingof the support beam 31, there is a somewhat greater distance between thetwo beams. As can be seen, the width of the contact surface (top of theledge 19') between the pressure cushion 32 and the channel wall support16 is unchanged as compared with FIG. 1. For the reasons indicatedabove, the support force exerted by the pressure cushion on the channelwall support 16 is the same in FIG. 1A as in FIG. 1. In other words,with respect to FIG. 1B, the supporting force exerted by the pressurecushion on the channel wall support 16 is constant over the entirelength of the beams 16 and 31.

In FIG. 2 there are symbolically indicated in dot-dash lines two wirescreens or wires 6 and 9 of a double-wire end of a paper making machine.The upper wire 6 slides along the bottom of ledges 5 which are rigidlyarranged in the machine. The lower wire 9 slides over a resilient ledge,designated generally as 50. It consists essentially of a ceramic headledge 51 which is fastened on a moveable beam 52; the latter is referredto below as the "moveable support ledge". Furthermore, a stationary beam53 is provided, referred to below as the "stationary guide ledge".Between the moveable support ledge 52 and the stationary guide ledge 53there is a pressure cushion 54. All of these parts extend transverse tothe direction of travel of the wire, and preferably over the entirewidth (about 2 to 10 meters) of the wires 6 and 9. The pressure cushion54, is again preferably developed as a tube.

The moveable support ledge 52 has in the center of its inner side aprojection 52' of approximately square cross section but rounded, whichcorresponds to the ledge 19' in FIG. 1.

A similar projection can also be provided on the stationary guide ledge53. Each of these projections forms a contact surface against which thepressure cushion 54 acted on by pressure rests.

The width b of each of the two contact surfaces is again less than thetotal width B of the pressure cushion 54. Furthermore, free spaces 55are provided on both sides of each contact surface, into which spacesthe lateral regions of the pressure cushion extend to a greater orlesser extent. As soon as the distance a between the contact surfacesbecomes less than shown in FIG. 2, each lateral region of the pressurecushion 54 forms a loop which fills out the free space 55 to a greateror lesser extent. In the extreme case as shown in FIG. 2A, the pressurecushion 54 is without pressure so that the moveable support ledge 52(together with the head ledge 51) is moved away from the wires 6 and 9.The free spaces 55 are limited inter alia by side surfaces 56 of theprojections 52' and 53'.

The distance a may change in operation; it may become greater or lesserthan what is shown in FIG. 2. This can take place, for instance, if theamount of fiber pulp introduced between the two wires 6 and 9 changes.In such case, with constant cushion pressure only a slight change in thesupport force transmitted takes place despite the deformation of thepressure cushion. In this way, the result is obtained that the forcewith which the ledge 50 is pressed against the lower wire 9 (and thusthe dewatering pressure in the pulp) remains unchanged. Furthermore,when the stationary guide ledge 53 bends and therefore when the distancea differs over the length of the guide ledge 53, the value of thesupporting force which the pressure cushion 54 exerts on the moveablesupport ledge 52 is nevertheless substantially more uniform over thelength thereof than in the case of the conventional constructions. It isthus unnecessary to provide a plurality of shorter pressure cushions ina row one behind the other and to act with different pressures on thesepressure cushions (known from FIG. 7 of the aforementioned WO 89/02499).If a plurality of shorter pressure cushions arranged in a row are usedin the construction of the invention, then all of these pressurecushions are acted on with the same pressure.

For the lateral guiding of the pressure cushion 54, it has twolongitudinal ribs 57 which engage in corresponding longitudinal groovesin the projections 52, 53. As can be seen, there is no stop which wouldlimit the stroke of the moveable ledge 50 in upward direction inoperation.

We claim:
 1. A hydraulic support device in a paper making machine incombination with and for supporting a first beam and a second beam,wherein the beams extend parallel to each other, each of the beamshaving two opposite ends, and further comprising means for coupling thebeams to each other at each of their respective two opposite ends andwithout the beams being coupled at locations along the beams which arebetween their opposite ends, the device comprising:the first beam havinga first contact surface extending over the length of the first beam andfacing toward the second beam; the second beam having a second contactsurface extending over the length of the second beam and facing towardthe first beam; pressure cushion means between and contacting the firstand the second contact surfaces for supporting the second beam on thefirst beam, the pressure cushion means having pressure fluid therein,the pressure of which is variable but which is uniform over the lengthof the pressure cushion means along the contact surfaces; means forcontrollably varying the pressure in the pressure cushion means duringoperation of the support device; and in the width direction across thefirst beam and the pressure cushion means, the second contact surfacehas a width substantially equal to a total width of the pressure cushionmeans, the first contact surface has a width less than the total widthof the pressure cushion means, the first contact surface being so shapedand the first beam at its region next to the contact surface and in thewidth direction being so shaped as to define a free space on each sidein the width direction of the first contact surface into which eachspace extends a part of the pressure cushion means that is beyond thewidth of the first contact surface.
 2. The hydraulic support device ofclaim 1 wherein the pressure cushion means comprises a tube with apressure fluid therein and extending over the length of the contactsurfaces.
 3. The hydraulic support device of claim 2, wherein the tubehas a cross section such that when the contact surfaces press againstthe tube, a loop of the tube is developed beyond each side of the firstcontact surface, each loop extending into the respective free space ateach side.
 4. The hydraulic support device of claim 3, furthercomprising guide walls on the second beam extending transversely to thesecond contact surface and spaced outward of the tube to laterallysupport the tube when it is deformed under pressure from the first andsecond contact surfaces, and also define the space for the loop of thetube.
 5. The hydraulic support device of claim 1, wherein there is atleast one of the pressure cushion means.
 6. The hydraulic support deviceof claim 1, wherein there is only one of the pressure cushion means. 7.The hydraulic support device of claim 1, wherein the pressure cushionmeans is of a length along the contact surfaces to extend up to theopposite ends of the beams.
 8. The hydraulic support device of claim 1,wherein the coupling means comprise flexurally elastic elements.
 9. Incombination, a paper making machine headbox and the hydraulic supportdevice of claim 1;the headbox comprising first and second flow guidewalls which define an outlet slot for pulp and the first wall beingmovable toward and away from the second wall; the first beam of thehydraulic support device being part of the first wall of the head box.10. The hydraulic support device of claim 1, further comprising guidewalls on the second beam extending transversely to the second contactsurface and spaced outward of the pressure cushion means to laterallysupport the pressure cushion means when it is deformed under pressurefrom the first and second contact surfaces.
 11. The hydraulic supportdevice of claim 10, wherein the guide walls are outward of the sides ofthe first contact surface.
 12. A hydraulic support device in a papermaking machine in combination with and for supporting a first moveablebeam and a second stationary beam, wherein the beams extend parallel toeach other, the device comprising:the first beam having a first contactsurface extending over the length of the first beam and facing towardthe second beam; the second beam having a second contact surfaceextending over the length of the second beam and facing toward the firstbeam; pressure cushion means between and contacting the first and thesecond contact surfaces for supporting the first beam on the secondbeam, the pressure cushion means having pressure fluid therein, thepressure of which is variable but which is uniform over the length ofthe pressure cushion means along the contact surfaces; means forcontrollably varying the pressure in the pressure cushion means duringoperation of the support device, wherein the pressure cushion meanssupports the first beam to be freely movable over the entire length ofthe first beam relative to the second beam and transversely to thelongitudinal direction of the beams under change in pressure in thepressure cushion means, such that as the first beam is moved, thedistance between the first and second surfaces varies along the lengthof the beams, but the pressure in the pressure cushion means supportingthe first beam is uniform along the length of the beams; and in thewidth direction across the first beam and the pressure cushion means, atleast the first contact surface has a width less than a total width ofthe pressure cushion means, the first contact surface being so shapedand the first beam at its region next to the contact surface and in thewidth direction being so shaped as to define a free space on each sidein the width direction of the first contact surface into which eachspace extends a part of the pressure cushion means that is beyond thewidth of the first contact surface.
 13. In combination, twin wires of apaper making machine and the hydraulic support device of claim 12, thewires being movable past the hydraulic support device, the first beam ofthe hydraulic support device defining a resilient support ledge for oneof the wires and wherein the beams extend across the wires moving past.14. The hydraulic support device of claim 12, wherein each of the firstand second contact surfaces is of a width less than the total width ofthe pressure cushion means under pressure from the contact surfaces,each of the beams having side surfaces at opposite sides of theirrespective contact surfaces in the width direction, the side surfaces ofeach beam extending away from the respective contact surface thereof andlimiting and defining the free space, whereby each side of each of therespective beam having the respective contact surface forms eachrespective free space.
 15. The hydraulic support device of claim 14,wherein the pressure cushion means comprises a tube having a pressurefluid therein and extending over the length of the contact surfaces, thetube having a cross section such that when the contact surfaces pressagainst the tube, a loop of the tube is developed beyond each of thesides surfaces of the beams to extend into each respective free space.16. The hydraulic support device of claim 12, further comprising atleast one longitudinal rib on the pressure cushion means extending alongat least the first contact surface, and at least the first contactsurface having a longitudinal groove into which the rib extends.
 17. Thehydraulic support device of claim 12, wherein the first beam includes aledge and the first contact surface is formed by the ledge.